Recently, substantial attention has been directed toward the development of lightweight tubular shafts for golf clubs and other articles such as fishing rods. Such shafts are commonly manufactured from sheets of composite materials, including, for example, various forms of "pre-preg." Pre-preg composite sheets are formed by pulling strands of fiber, for example, carbon or glass fiber, through a resin solution and allowing the resin to partially cure. Exemplary resins or "binding matrices" may include, for example, thermoset epoxy resins and thermo-plastic resins. Alternatively, pre-preg sheets may be manufactured by pulling a fabric or weave of composite fiber through a resin solution and allowing the resin to partially cure. In either case, once the resin is partially cured or "staged," the resin holds the fibers together such that the fibers form a malleable sheet When using pre-preg sheets, shafts generally may be manufactured by wrapping a set of plies of pre-preg composite sheet around a mandrel in a predetermined manner, wrapping the ply-wrapped mandrel in a binding material such as cellophane or polypropylene tape, and heating the ply-wrapped mandrel to a predetermined temperature for a time sufficient to allow the resin in the pre-preg composite sheets to become fully cured. Once the resin has been fully cured, the binding material may be removed from the exterior of the shaft, and the mandrel may be removed from the core of the shaft.
Alternatively, a set of plies of pre-preg composite sheet may be wrapped around a bladder covered mandrel, and placed in a mold. If desired, the mandrel may be removed leaving the bladder and plies in the mold, or the mandrel may be left in the mold. In either case, the bladder may be inflated to a predetermined pressure to force the plies of pre-preg against the walls of the mold, and the mold may be heated to a predetermined temperature for a time sufficient to allow the resin in the pre-preg composite sheets to completely cure. Once the resin has been cured, the cured plies (shaft) and mandrel may be removed from the mold, and the bladder (and mandrel if not previously removed) may be removed from the shaft. The resulting shaft may then be used to manufacture such articles as golf clubs and fishing poles.
When assembling golf clubs or fishing poles, a handle or grip, made from rubber, leather, cork or similar materials, generally will be placed on one end of the shaft. Such grips generally provide a tacky or slip-resistant surface which enables a person to securely grasp the golf club or fishing rod and minimizes the likelihood that the golf club or fishing rod will slip out of or change position within the person's hands during use.
Often, the grip provided may comprise a substantially cylindrical sleeve having an open end and a substantially closed end. The sleeve is introduced over the end of the shaft and extends longitudinally over a portion of the shaft such that the closed end of the grip engages the end of the shaft. The grip generally may be fixed on the shaft by friction and/or through the use of conventional adhesives or adhesive tapes.
Alternatively, a wrapped tape grip may be used. Rubber or similar tape material, commercially available in rolls and possibly having a backing adhesive, may be helically wound over the end of a shaft. Then, a cap may be placed over the end of the shaft, holding the end of the tape and keeping it from potentially unwinding.
Conventional grips, however, may add substantial and undesired weight to the shaft overall, or may add weight in a location that is not optimal for the design of a particular article. For example, in the case of golf clubs it is sometimes a goal to substantially reduce the overall weight of a shaft, or to move weight from an end of the shaft to another location. Weight reduction or weight shifting in a golf club shaft is limited, however, by the need to provide a grip on the end of the shaft, with traditional grips adding between about 45-50 grams to the weight of the shaft, and ultra-light grips adding about 20 grams.
Accordingly, it is believed that those in the field of golf club design would find a substantially reduced weight grip that is both durable and economical to manufacture to be quite useful. It is also believed that methods of forming a reduced weight grip on the end of a shaft for a golf club would be found to be useful.